CRAIG’S SOIL MECHANICS

CONTENTS

Part 1 Development of a mechanical model for soil 1
1 Basic characteristics of soils 3
1.1 The origin of soils 3
1.2 The nature of soils 6
1.3 Plasticity of fine-grained soils 10
1.4 Particle size analysis 13
1.5 Soil description and classification 14
1.6 Phase relationships 22
1.7 Soil compaction 26

2 Seepage 39
2.1 Soil water 39
2.2 Permeability and testing 41
2.3 Seepage theory 46
2.4 Flow nets 51
2.5 Anisotropic soil conditions 57
2.6 Non-homogeneous soil conditions 59
2.7 Numerical solution using the Finite Difference Method 60
2.8 Transfer condition 63
2.9 Seepage through embankment dams 64
2.10 Filter design 73

3 Effective stress 79
3.1 Introduction 79
3.2 The principle of effective stress 80
3.3 Numerical solution using the Finite Difference Method 83
3.4 Response of effective stress to a change in total stress 83
3.5 Effective stress in partially saturated soils 87
3.6 Influence of seepage on effective stress 87
3.7 Liquefaction 91

4 Consolidation 101

4.1 Introduction 101
4.2 The oedometer test 102
4.3 Consolidation settlement 109
4.4 Degree of consolidation 112
4.5 Terzaghi’s theory of one-dimensional consolidation 115
4.6 Determination of coefficient of consolidation 121
4.7 Secondary compression 126
4.8 Numerical solution using the Finite Difference Method 127
4.9 Correction for construction period 131
4.10 Vertical drains 136
4.11 Pre-loading 140

5 Soil behaviour in shear 145
5.1 An introduction to continuum mechanics 145
5.2 Simple models of soil elasticity 149
5.3 Simple models of soil plasticity 152
5.4 Laboratory shear tests 156
5.5 Shear strength of coarse-grained soils 168
5.6 Shear strength of saturated fine-grained soils 174
5.7 The critical state framework 183
5.8 Residual strength 188
5.9 Estimating strength parameters from index tests 189

6 Ground investigation 201
6.1 Introduction 201
6.2 Methods of intrusive investigation 203
6.3 Sampling 210
6.4 Selection of laboratory test method(s) 215
6.5 Borehole logs 216
6.6 Cone Penetration Testing (CPT) 218
6.7 Geophysical methods 222
6.8 Contaminated ground 227

7 In-situ testing 231
7.1 Introduction 231
7.2 Standard Penetration Test (SPT) 232
7.3 Field Vane Test (FVT) 236
7.4 Pressuremeter Test (PMT) 240
7.5 Cone Penetration Test (CPT) 252
7.6 Selection of in-situ test method(s) 260

Part 2 Applications in geotechnical engineering 267
8 Shallow foundations 269
8.1 Introduction 269
8.2 Bearing capacity and limit analysis 271
8.3 Bearing capacity in undrained materials 273
8.4 Bearing capacity in drained materials 285
8.5 Stresses beneath shallow foundations 295
8.6 Settlements from elastic theory 300
8.7 Settlements from consolidation theory 304
8.8 Settlement from in-situ test data 311
8.9 Limit state design 316

9 Deep foundations 327
9.1 Introduction 327
9.2 Pile resistance under compressive loads 331
9.3 Pile resistance from in-situ test data 340
9.4 Settlement of piles 341
9.5 Piles under tensile loads 349
9.6 Load testing 350
9.7 Pile groups 353
9.8 Negative skin friction 358

10 Advanced foundation topics 365
10.1 Introduction 365
10.2 Foundation systems 366
10.3 Shallow foundations under combined loading 380
10.4 Deep foundations under combined loading 389

11 Retaining structures 403
11.1 Introduction 403
11.2 Limiting earth pressures from limit analysis 404
11.3 Earth pressure at rest 415
11.4 Gravity retaining structures 418
11.5 Coulomb’s theory of earth pressure 429
11.6 Backfilling and compaction-induced earth pressures 434
11.7 Embedded walls 436
11.8 Ground anchorages 447
11.9 Braced excavations 452
11.10 Diaphragm walls 456
11.11 Reinforced soil 458

12 Stability of self-supporting soil masses 467
12.1 Introduction 467
12.2 Vertical cuttings and trenches 468
12.3 Slopes 472
12.4 Embankment dams 487
12.5 An introduction to tunnels 490

13 Illustrative cases 501
13.1 Introduction 501
13.2 Selection of characteristic values 502
13.3 Field instrumentation 506
13.4 The observational method 514
13.5 Illustrative cases 515